1. Technical Field
This invention relates to quality control and quality assurance in a laboratory. More specifically, the invention relates to assuring and controlling quality of equipment and personnel in a laboratory.
2. Description of the Prior Art
Quality control in the clinical laboratory is an accepted component of maintaining a standard of operation for laboratory equipment. It is mandated by the federal government and all major laboratory accrediting organizations. Quality controls are samples of assayed materials of known values as established by repetitive analysis. In the clinical laboratory, these samples are processed at periodic intervals in a manner that approximates patient testing. Quality control samples must be run at more than one concentration level. The stated values of controls are used as target values. Control results are analyzed using statistical parameters to determine if an instrument and/or reagent system is in control for a given run of patient test results. A variety of complex statistical methods exist for determination of acceptability of quality control results prior to releasing patient test results. Control results are recorded and plotted on charts and evaluated by technical staff to detect problems and trends in sample testing.
Modern quality control theory is predicated on the assumption that quality controls are to be performed at a frequency within which the accuracy and precision of the measuring system is expected to be stable based upon manufacturer's recommendations. However, both random and systematic errors are known to occur at some level of frequency within any given testing system. The goal of quality control is to detect these errors before false patient test results are released. Standard practices of quality control in today's clinical laboratory appears to be biased. The biases occur because the interval at which controls are run are generally pre-determined and defined by a given laboratory in a manner which is arbitrary or based upon convenience. To eliminate these biases, controls should be run in a completely random manner. It is prescribed that control samples should be tested in the same manner as patient specimens. Current biases in quality control methods with regard to time interval and position placement prevent simulation of actual patient testing conditions by controls.
In a hospital laboratory, it is common practice to run quality controls at the beginning of each shift. Some laboratories run quality controls at a defined interval between patient samples. Environmental conditions such as temperature, humidity, electrical source variation, and other factors may vary during the time period in which patient samples are tested. Failure to move quality controls around over time may result in failure of quality controls to detect testing problems. Most modern laboratory instruments are configured in a manner that accommodates running multiple patient samples at a given time. Common instrument configurations adapted to receive multiple test samples include testing wheels, racks, and plates with multiple wells. Since patient samples may be run in any of the positions on an instrument, it is logical that quality control samples should have an equal chance of being placed in any position to more accurately simulate actual patient testing conditions. In fact, some instrument manufacturers have included internal wells or vessels for storage of control materials that are separate from the portion of the instrument within which patient samples are placed for testing. Although this may be convenient to the technologist, it clearly does not simulate actual patient testing conditions. The chemical reaction may be identical, but the mechanical steps that precede the reactions clearly are not. Random placement of control materials in any of the positions on an instrument for which patient samples have a chance of being placed more closely simulates actual patient testing conditions. Accordingly, there is a need for a method for randomly selecting a position in which to place a control sample on a given instrument.
Ideally, randomization of as many variables as possible should provide the closest simulation of quality control testing to actual patient testing conditions. For a variety of reasons, it may not be practical or possible to randomize all variables at one time and still perform controls in a way that will allow review prior to releasing patient test results. However, by randomly selecting among several factors that contribute to proper operation of the laboratory equipment, a laboratory will be able to perform quality control in a manner that closely simulates actual patient testing conditions.
In addition to physical placement of a quality control on a laboratory instrument to insure proper function of the equipment, there is also a factor of human error that must be acknowledged. Cross training of technologists is common practice in today's clinical laboratory. Multiple operators may be performing testing on one instrument at any given time. It is necessary for operators to maintain competency and adequate skill levels on all equipment that they may be using for patient testing. Randomization of operator scheduling assures ongoing experience in all areas for which the operator may be required to work. One method of competency testing is to randomly repeat tests for patient samples by a second skilled individual. One method of maintaining quality assurance is to repeat the work by a second skilled individual and to compare the results for agreement. Accordingly, there is a need to periodically assess the skills and competency of operators in an unbiased manner.